Molecular formula examples

Class FunctlonsI Group Molecular Formula Example Compound Name... 

More than one stable substance can correspond to a given molecular formula. Examples are butane and 2-methylpropane (isobutane), each of which has the molecular formula C4H10. Similarly, methoxymethane (dimethyl ether) and ethanol have the same formula, C2H60 ... 

Molecular Formula Example compound Number of Isomers... 

Determining the molecular formula from percentage composition and molecular weight Given the empirical formula and molecular weight of a substance, obtain its molecular formula. (EXAMPLE 3.12)... 

In the introduction we noted that both Berzelius and Wohler were fascinated by the fact that two different compounds with different properties ammonium cyanate and urea pos sessed exactly the same molecular formula CH4N2O Berzelius had studied examples of similar phenomena earlier and invented the word isomer to describe different compounds that have the same molecular formula... 

Cycloalkanes are alkanes that contain a ring of three or more carbons They are fre quently encountered m organic chemistry and are characterized by the molecular formula C H2 Some examples include... 

When the objective is analytical the products of ozonolysis are isolated and identi lied thereby allowing the structure of the alkene to be deduced In one such example an alkene having the molecular formula C Hig was obtained from a chemical reaction and was then subjected to ozonolysis giving acetone and 2 2 dimethylpropanal as the products... 

The classification of hydrocarbons as aliphatic or aromatic took place m the 1860s when It was already apparent that there was something special about benzene toluene and their derivatives Their molecular formulas (benzene is CgHg toluene is C7Hj ) indicate that like alkenes and alkynes they are unsaturated and should undergo addition reac tions Under conditions m which bromine for example reacts rapidly with alkenes and alkynes however benzene proved to be inert Benzene does react with Bi2 m the pres ence of iron(III) bromide as a catalyst but even then addition isn t observed Substitu tion occurs instead ... 

A second example concerns different compounds that have the same molecular weight but different molecular formulas such as heptane and cyclopropyl acetate... 

Atoms combine in definite proportions to give molecules. For example, natural gas is mostly composed of methane, a substance in which four hydrogen atoms (H) are combined with one carbon (C) the molecular formula is written as CH4. Similarly, water, ammonia, ethanol, and glucose have... 

Class Example Molecular formula CAS Registry Number Stmcture number... 

If the CH balance given by the CH multiplicities differs from the number of H atoms in the molecular formula, then the additional H atoms are bonded to heteroatoms. The C NMR spectra in Fig. 2.5 show, for example, for isopinocampheol (2), Cio// 0, a quaternary C atom (C), four CH units (C4//4), two CH2 units C2H4) and three CH3 groups (C3//5). In the C//balance, Cvfln, one H is missing when compared with the molecular formula, Cio// 0 to conclude, the compound contains one OH group. 

The answer to the first question is that you cannot easily calculate the number of isomers. The data in Table 2.1 were determined by a mathematician who concluded that no simple expression can calculate the number of isomers. The best way to ensure that you have written all the isomers of a par ticular- molecular- formula is to work systematically, beginning with the unbranched chain and then shortening it while adding branches one by one. It is essential that you be able to recognize when two different-looking structural formulas are actually the sane molecule written in different ways. The key point is the connectivity of the car bon chain. For example, the following group of structural... 

Isomers are substances having the same molecular formula and molecular weight, but differing in physical and chemical properties. Since branched and straight-chain alkanes with the same molecular formula can exist as distinct structures having different geometrical arrangement of the atoms, they are termed structural isomers. One example is C H,j (butane) which has two isomers ... 

The word carbohydrate derives historically from the fact that glucose, the first simple carbohydrate to be obtained pure, has the molecular formula C6H,206 and was originally thought to be a "hydrate of carbon, C6(Tl20)6." This view was soon abandoned, but the name persisted. Today, the term carbohydrate is used to refer loosely to the broad class of polyhydroxvlated aldehydes and ketones commonly called sugars. Glucose, also known as dextrose in medical work, is the most familiar example. 

The molar mass of acetic acid, as determined with a mass spectrometer, is about 60 g/mol. Using that information along with the simplest formula found in Example 3.6, determine the molecular formula of acetic acid. 

Allotropy is a very common phenomenon shown by metals, metalloids, and nonmetals. In the gaseous or liquid state, allotropes most often differ from one another in molecular formula. Consider, for example, the two allotropes of gaseous oxygen, 02, and ozone, 03. 

The number and kinds of atoms in a molecule can also be shown in a molecular formula. For example, the water molecule is symbolized H20. In this molecular formula, H means hydrogen atom, O means oxygen atom, and the subscript 2 following H indicates there are two hydrogen atoms bound to the single oxygen atom. The molecular formula of ammonia, NH3, indicates that one molecule of ammonia contains one atom of nitrogen (N) and... 

Table 2.1 may be useful for calculating the number of carbon, bromine, chlorine, and sulfur atoms in the molecular formula. This table shows that for every 100 12C atoms there are 1.1 13C atoms. Also, for every 100 32S atoms, there are 0.8 33S atoms and 4.4 34S atoms. The following examples... 

EXAMPLE F.3 Sample exercise Determining the molecular formula from the empirical formula... 

J 3 Determine the molecular formula of a compound from its empirical formula and its molar mass (Example F.3). 

The language of chemistry is understood better when the symbols of the more common elements are known, such as those shown on the following page. Use of these symbols provides a convenient shorthand method for chemists to represent molecular formulae. In these formulae, the subscript number following the atomic symbol denotes how many atoms of that element are in the molecule, for example, the formula for water is H2O, which means each molecule of water contains two atoms of hydrogen (symbol H) and one atom of oxygen (symbol O). 

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